This invention was made in the course of, or under, a contract with the United States Energy Research and Development Administration. It relates in general to the preparation of powders and, more particularly, to the preparation of finely divided metal, oxide, and metal-metal oxide mixtures. Finely divided metal powders are useful in conventional powder metallurgical techniques. Finely divided oxide powders are useful in the manufacture of coating compositions, intricately shaped and fine-grained ceramics, cermets, etc. Small particles and particularly important in the preparation of powder mixtures. In general, the smaller the particle size, the more uniform are the compositions and mechanical properties of metal, ceramic and cermet articles prepared from the powder mixtures.
Small oxide and metal particles are particularly useful in the manufacture of nuclear components. For example, the nuclear properties of ceramic or cermet neutron absorbers are directly related to the uniformity of composition of a material. The neutron dosimeter wires described in commonly assigned U.S. Pat. No. 3,971,944 contain as little as 0.1 wt. % of a target oxide in a diluent oxide. These oxide wires are extruded from an oxide powder mixture containing a binder. To ensure reproducible measurements, the composition in such wires must have a variance no more than + 1 wt. % at the 95% confidence level along the length of the wire. In order to ensure this uniformity at low target oxide concentrations, the oxide particles should be very small, e.g. 0.2-0.5 micron in diameter (equivalent area diameter).